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JSON Lines (a.k.a. newline-delimited JSON) is a simple
format for storing sequences of JSON values in which each value is serialized
on a single line and terminated by a newline sequence. The serde-jsonlines
crate provides functionality for reading & writing these documents (whether all
at once or line by line) using serde's serialization & deserialization
features.
Basic usage involves simply importing the BufReadExt or WriteExt extension
trait and then using the json_lines() or write_json_lines() method on a
BufRead or Write value to read or write a sequence of JSON Lines values.
Convenience functions are also provided for the common case of reading or
writing a JSON Lines file given as a filepath.
At a lower level, values can be read or written one at a time (which is useful
if, say, different lines are different types) by wrapping a BufRead or
Write value in a JsonLinesReader or JsonLinesWriter and then calling the
wrapped structure's read() or write() method, respectively.
When the async feature is enabled, analogous types for working with JSON
Lines asynchronously under tokio become available.
use serde::{Deserialize, Serialize};
use serde_jsonlines::{json_lines, write_json_lines};
use std::io::Result;
#[derive(Debug, Deserialize, Eq, PartialEq, Serialize)]
pub struct Structure {
pub name: String,
pub size: i32,
pub on: bool,
}
fn main() -> Result<()> {
let values = vec![
Structure {
name: "Foo Bar".into(),
size: 42,
on: true,
},
Structure {
name: "Quux".into(),
size: 23,
on: false,
},
Structure {
name: "Gnusto Cleesh".into(),
size: 17,
on: true,
},
];
write_json_lines("example.jsonl", &values)?;
let values2 = json_lines("example.jsonl")?.collect::<Result<Vec<Structure>>>()?;
assert_eq!(values, values2);
Ok(())
}